Ferromagnetism as a universal feature of inorganic nanoparticles

Sundaresan, A.; Rao, C. N. R.

doi:10.1016/j.nantod.2008.10.002

Cited by 414 publications

(262 citation statements)

References 71 publications

(80 reference statements)

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“…One of the more surprising recent incarnations of such novel magnetic behavior is the observation of magnetic properties in nanoscaled materials which are diamagnetic (i.e., nonmagnetic) in the bulk. This type of behavior has been observed in metal oxide nanoparticles and nanocrystalline films [16,17], as well as typically paramagnetic (e.g., Pd [18][19][20][21][22][23]) and diamagnetic (Cu, Ag, Pt [24,25]) metal nanostructures. The latter include gold-based nanostructures, which will be the topic of this review.…”

Section: Introductionmentioning

confidence: 69%

“…The anhysteretic magnetization vs. field loop was interpreted in the context of superparamagnetism. This magnetic phase can be explained in terms of coupled spins which are fluctuating due to the randomizing effect of temperature [16,17,69]. This work pointedly highlighted the remarkable difference nanoscale gold may have with the bulk state, most noticeably by highlighting the presence of unpaired coupled magnetic moments.…”

Section: Experimental Studiesmentioning

confidence: 94%

“…When thermal energy is sufficient to overcome the energy barrier that maintains the magnetic moments along a given direction, the particle becomes superparamagnetic and the particle's large moment fluctuates [16,17,69]. This barrier is known as the anisotropy energy barrier and is proportional to the product of the anisotropy constant K and the volume V of the nanoparticle.…”

Section: Experimental Studiesmentioning

confidence: 99%

See 2 more Smart Citations

Unexpected magnetism in gold nanostructures: making gold even more attractive

Trudel

2011

Gold Bull

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Gold nanostructures have attracted widespread attention due to their novel optical, electronic, and biocompatible properties. These make gold nanostructures (and in particular nanoparticles) very attractive for a variety of applications, including catalysis, therapeutics, diagnostics, sensing, and nanoelectronics. In this topical review, the newly discovered magnetic properties of gold nanostructures are highlighted. This unexpected magnetism in gold nanoparticles is a result of (1) the predominant effect of surfaces at the nanoscale, (2) the electronic modification to gold from strongly capping molecules, and (3) the strong spin-orbit coupling of gold. This review discusses the salient experimental results, a theoretical model, and closes by highlighting possible industrial applications of magnetic gold nanostructures.

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Section: Introductionmentioning

confidence: 69%

Section: Experimental Studiesmentioning

confidence: 94%

Section: Experimental Studiesmentioning

confidence: 99%

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Unexpected magnetism in gold nanostructures: making gold even more attractive

Trudel

2011

Gold Bull

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“…It has been suggested by Sundaresan et al (1,2) that room-temperature ferromagnetism (RTFM) is exhibited universally by inorganic NPs due to exchange between electron spin moments caused by oxygen vacancies (V O ). Ge et al (3) theorized and verified in experiment that V O causes a significant increase in magnetization of NPs over bulk samples, and that V O affects the surrounding f electrons , causing a net magnetic moment for the particles.…”

Section: Introductionmentioning

confidence: 99%

Concentration dependence of magnetic moment in Ce1-xFexO2

Beausoleil

Thurber

Rao

et al. 2012

Journal of Applied Physics

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In this study, we examined the impact of iron doping on the structural, chemical, and magnetic properties of ceria (Ce 1-x Fe x O 2 ). Samples were produced in triplicate through a coprecipitation approach in a forced hydrolysis synthesis that yielded consistently sized nanocrystals, using three different cerium precursors: cerium chloride, cerium ammonium nitrate and cerium nitrate. Particles were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy and vibrating sample magnetometry (VSM). XRD showed the average crystallite size to be 4.4 ± 1.2 nm, which agreed well with TEM data. XPS and EPR data shows iron to be in the Fe 3+ state and confirms the nominal dopant concentration. The moment per Fe ion found was largest at the lowest dopant concentrations, with values of 0.078 and 0.055 µ B /Fe ion for 0.1 and 0.5% Fe, respectively, which quickly decreased as the concentration was increased. We used XPS to estimate Ce 3+ /Ce 4+ ratio to be in the 0.2-0.3 range and observed a linear relation between the saturation magnetization and the Ce 3+ /Ce 4+ ratio.Introduction:

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“…Another inherent feature of nanomaterials is a very high surface area, which promotes better interaction between the particles and the medium 5 . Among several possible morphologies, equiaxial nanoparticles present a lot of applications in chemistry, physics, engineering, and medicine, among other fields [6][7][8][9] .…”

Section: Introductionmentioning

confidence: 99%

Chemical modification of cobalt ferrite nanoparticles with possible application as asphaltene flocculant agent

et al. 2013

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Asphaltenes can cause enormous losses in the oil industry, because they are soluble only in aromatic solvents. Therefore, they must be removed from the petroleum before it is refined, using flocculant agents. Aiming to find new materials that can work as flocculant agents to asphaltenes, cobalt ferrite nanoparticles were chemically modified through acid-base reactions using dodecylbenzene sulfonic acid (DBSA) to increase their lipophilicity. Nanoparticle synthesis was performed using the co-precipitation method followed by annealing of these nanoparticles, aiming to change the structural phase. Modified and unmodified nanoparticles were tested by FTIR-ATR, XRD and TGA/DTA. In addition, precipitation onset of the asphaltenes was performed using modified and unmodified nanoparticles. These tests showed that modified nanoparticles have a potential application as flocculant agents used to remove asphaltenes before oil refining, since the presence of nanoparticles promotes the asphaltene precipitation onset with the addition of a small amount of non-solvent.

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Ferromagnetism as a universal feature of inorganic nanoparticles

Cited by 414 publications

References 71 publications

Unexpected magnetism in gold nanostructures: making gold even more attractive

Unexpected magnetism in gold nanostructures: making gold even more attractive

Concentration dependence of magnetic moment in Ce1-xFexO2

Chemical modification of cobalt ferrite nanoparticles with possible application as asphaltene flocculant agent

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